Iron is essential for the body to function and has a crucial role in transporting oxygen - low levels cause anaemia which leads to tiredness and lethargy.

Iron tablets, which are available over the counter or on prescription, are taken by millions of people around the world.

For the study, researchers from Imperial College in UK used human endothelial cells, which line blood vessels, and added a placebo or an iron solution of 10 micromolar (a similar concentration to that seen in the blood after taking an iron tablet).

Through looking at genes used within cells, and then examining the cells in more detail, they found that within 10 minutes, cells treated with the iron solution had activated DNA repair systems. These were still activated six hours later.

The amount of iron given in standard treatments, such as tablets and infusions, and the effects this could be having on the body needs to be carefully looked at, researchers said.